硫脲改性磁性壳聚糖微球对Hg^(2+),Cu^(2+)和Ni^(2+)的吸附

Adsorption of Hg^(2+),Cu^(2+) and Ni^(2+) by Magnetic Chitosan Microspheres Modified Using Thiourea

利用反相分散-化学交联的方法制备磁性壳聚糖微球(MCS).并利用硫脲改性,得到改性磁性壳聚糖微球(TMCS)。考察接触时间、pH 值、温度以及金属离子初始浓度对 TMCS 吸附 Hg^(2+),Cu^(2+)和Ni^(2+)的影响。发现相同条件下,Hg^(2+),Cu^(2+)和 Ni^(2+)达到吸附平衡的时间依次增加,饱和吸附容量随pH 值和金属离子初始浓度的增高而增加,随温度升高而下降。利用拟一级反应动力学模型和拟二级反应动力学模型对实验数据进行拟合,并分别采用 Freundlich 模型、Langmuir 模型和 Tempkin 模型对吸附等温线进行拟合。结果表明,吸附动力学符合拟二级反应动力学模型,化学吸附为控制步骤,且吸附等温线用 Langmuir 模型拟合结果最好。在 TMCS 1.5 g/L,金属离子初始浓度100 mg/L,pH 值5.0和吸附6 h条件下,TMCS 对 Hg^(2+),Cu^(2+)和 Ni^(2+)饱和吸附容量分别为625.2,66.7和15.3 mg/g。吸附金属离子的TMCS 利用0.01 mol/L 的乙二胺四乙酸(EDTA)再生,金属离子脱附率高于85%。

Magnetic chitosan microspheres were prepared by inverse phase dispersion and chemical cross-linking method, and then chemically modified using thiourea for adsorption of metal ions. Effects of contact time, temperature, pH and initial concentration on the adsorption of Hg^2＋ , Cu^2＋ and Ni^2＋ by the magnetic chitosan microspheres modified using thiourea （TMCS） were investigated. It was found that under the same conditions, the equilibrium adsorption time of Hg^2＋ , Cu^2＋ and Ni^2＋ increased successively, and the adsorption capacity of the metal ions increased with the increase of pH and initial concentration of the metal ions, but decreased with the increase of temperature. The kinetics was evaluated utilizing the pseudo-first-order reaction and pseudo-second-order reaction models, and the equilibrium data were analyzed using the Langmuir, Freundlich and Tempkin isotherm models. The results showed that the adsorption kinetics followed the mechanism of the pseudo-second-order reaction equation, which evidenced that chemical adsorption was the rate-limiting step. The equilibrium data were fitted with Langmuir isotherm well. Under the conditions of TMCS 1.5 g/L, metal ions initial concentration 100 mg /L, pH 5. 0 and adsorption time 6 h, the maximum adsorption capacities of Hg^2＋ , Cu^2＋ and Ni^2＋ were 625.2, 66.7 and 15.3 mg/g respectively, and the desorption of metal ions absorbed by TMCS could reach above 85% by 0.01 mol/L ethylenediamine tetraacetic acid （EDTA）.